1. Field of the Invention
The present invention relates to a liquid ejection head that ejects a liquid and a method of producing the liquid ejection head, in particular, an ink jet recording head that ejects ink onto a recording medium to perform recording and a method of producing the ink jet recording head.
2. Description of the Related Art
Liquid ejection heads that eject liquids are specifically exemplified by ink jet recording heads each of which is applied to an ink jet recording system according to which ink is ejected onto a recording medium so that recording is performed.
Japanese Patent Application Laid-Open No. 2004-351754 has the following description concerning the production of an ink jet recording head. First, the top of a silicon substrate is provided with multiple ejection pressure generating elements and electrode terminals for electrically connecting the elements to the outside. After that, a resist is patterned so as to occupy portions serving as ink flow paths. Further, the top of the resist is provided with ink flow path wall members, and then ink ejection orifices are patterned. Next, the ink flow path wall members are cured and then the resultant is perforated with holes for supplying ink from the back surface side of the silicon substrate to ejection element portions. After that, the resist is removed. Thus, the ink flow paths and the ink ejection orifices are completed. Then, a recording element (chip) obtained by cutting the silicon substrate into a chip shape with a size required for the ink jet recording head is attached to a supporting member. After that, plating is conducted or a ball bump is formed on a pad in order that an electrical wiring board that supplies power from the outside of the head to the ink ejection pressure generating elements and the like are joined. Then, the electrical wiring board having a lead wiring is joined, and a lead sealing material that seals electrical connection portions is applied from above the board. The lead sealing material is required not only to seal the electrical connection portions but also not to cause peeling-off even by rubbing with, for example, a blade or wiper which is placed in a printer to clean the surface provided with the ink ejection orifices at the uppermost surface of a head substrate or by contact with paper or the like caused by a paper jam. Accordingly, the lead sealing material is preferably a high-hardness material.
Meanwhile, Japanese Patent Application Laid-Open No. H11-348290 describes a method involving joining an ink flow path wall member formed of an epoxy resin composition to a silicon substrate through a contact layer formed of a polyether amide resin in order that adhesion between the silicon substrate and the ink flow path wall member is maintained for a long time period.
However, a lead sealing material applied to an electrical connection portion of an ink jet recording head formed by the method described in Japanese Patent Application Laid-Open No. H11-348290 may become in contact with an interfacial portion between the ink flow path wall member and the contact layer. As the lead sealing material is typically heat-curable, the lead sealing material penetrates the interface between the ink flow path wall member and the contact layer when heating for curing is performed, and as a result, the ink flow path wall member peels off in some cases. This is probably because of the following reason. In general, the ink flow path wall member and the lead sealing material are each formed of an epoxy resin composition, and hence have close solubility parameter values (SP values). That is, the above-mentioned penetration occurs probably because an affinity between the ink flow path wall member and the lead sealing material is higher than an affinity between the ink flow path wall member and the contact layer.